Kimura & Kohara: F58 Early recruitment

Motor unit potentials (MUPs) recorded from the biceps brachii (BB) during voluntary contraction in a patient with mitochondrial encephalomyopathy. An early recruitment during a slight muscle contraction readily leads to MUP overlap. The tracing contains long-duration polyphasic potentials as well as small potentials derived from a single muscle fiber. The polyphasic potentials seen during the weakest muscle contraction show an unstable waveform.